Williams was beaten by Carl Baker in last year's Prizefighter competition
Danny Williams has pulled out of his British heavyweight title defence against Derek Chisora on 13 February, blaming a viral infection.
The fight at Wembley Arena had already been hit by the withdrawal of Williams' original opponent Sam Sexton.
He was replaced by the unbeaten Chisora after cutting his hand in training.
Promoter Frank Warren says he is now in talks with two boxers who hold wins over Williams and may be able to step in at short notice.
Chisora had been due to meet Williams last year but was suspended after biting opponent Paul Butlin on 22 May.
He was banned for four months and fined £2,500 for the incident which took place at York Hall in Bethnal Green but returned in October to stop Georgia's Zurab Noniashvili in the eighth round.
The Zimbabwe-born fighter is rated as one of the brightest prospects in the British heavyweight division.
Chisora had been due to meet another veteran, Matt Skelton, for the Southern Area title on the Williams-Sexton undercard.
Londoner Williams, 36, with eight defeats in 50 fights, had said he planned to retire after fighting Chisora.
February's 'Night of Champions' bill also features British stars Kevin Mitchell, Kell Brook, Nathan Cleverly, James DeGale and Frankie Gavin.
Warren said: "I am working hard for Derek who will still feature on the 'Night of the Champion' show.
"I said last week that Danny should vacate the title or retire if he didn't want to fight him."